The polyphenylene ether resins are a family of engineering thermoplastics that are well known to the polymer art. These polymers may be made by a variety of catalytic and non-catalytic processes from the corresponding phenols or reactive derivatives thereof. By way of illustration, certain of the polyphenylene ethers are disclosed in Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875, and in Stamatoff, U.S. Pat. Nos. 3,257,357 and 3,257,358. In the Hay patents, the polyphenylene ethers are prepared by an oxidative coupling reaction comprising passing an oxygen-containing gas through a reaction solution of a phenol and a metal-amine complex catalyst. Other disclosures relating to processes for preparing polyphenylene ether resins, including graft copolymers of polyphenylene ethers with styrene type compounds are found in Fox, U.S. Pat. No. 3,356,761; Sumitomo, U.K. Pat. No. 1,291,609; Bussink et al, U.S. Pat. No. 3,337,499; Blanchard et al, U.S. Pat. No. 3,219,626; Laakso et al, U.S. Pat. No. 3,342,892; Borman, U.S. Pat. No. 3,344,166; Hori et al, U.S. Pat. No. 3,384,619; Faurote et al U.S. Pat. No. 3,440,217; and disclosures relating to metal based catalysts which do not include amines, are known from patents such as Wieden et al, U.S. Pat. No. 3,442,885 (copper-amidines); Nakashio et al, U.S. Pat. No. 3,573,257 (metal-alcoholate or -phenolate); Kobayashi et al, U.S. Pat. No. 3,445,880 (cobalt chelates); and the like. In the Stamatoff patents, the polyphenylene ethers are produced by reacting the corresponding phenolate ion with an initiator, such as peroxy acid salt, an acid peroxide, a hypohalite, and the like, in the presence of a complexing agent. Disclosures relating to non-catalytic processes, such as oxidation with lead dioxide, silver oxide, etc., are described in Price et al U.S. Pat. No. 3,382,212. Cizek, U.S. Pat. No. 3,383,435 discloses polyphenylene etherstyrene resin compositions. All of the above-mentioned disclosures are incorporated by reference.
The term "polystyrene resin" includes polymers and copolymers of styrene, alpha methyl styrene, chlorostyrene, and the like, and also high-impact polystyrene, also known in the art as HIPS, see Science, p. 817 Vol. 208, May 23, 1980, which is a rubber modified polystyrene.
In the prior art, rubber-modified styrene resins have been admixed with polyphenylene ether resins to form compositions that have modified properties. The Cizek patent, U.S. Pat. No. 3,383,435, discloses rubber-modified styrene resin-polyphenylene ether resin compositions wherein the rubber component is of the unsaturated type such as polymers and copolymers of butadiene. The physical properties of these compositions are such that it appears that many of the properties of the styrene resins have been upgraded, while the moldability of the polyphenylene ethers are improved.
Rubber modified high impact polystyrenes are commercially available under the trade names Amoco 6H6, from the Amoco Company; FG-834 from the Foster Grant Co., and HT-91 from Monsanto Company. These, in general, are polystyrene modified with polybutadiene rubber. The preferred HIPS is Amoco 6H6.
In U.S. Pat. No. 3,737,479 it is disclosed that the addition of silicone oils to polyphenylene oxide or to polyphenylene oxide-polystyrene blends, preferably a rubber modified high impact polystyrene (See Example 1) improves Gardner impact strength but does not affect the Izod impact strength. It is stated, col. 6, lines 48 to 54 of the patent: "In a preferred embodiment of the invention, there is incorporated a polyolefin into the composition. This enhances Izod impact strengths and processability without reducing other properties. Suitable polyolefins include, polyethylene, polypropylene and ethylene-propylene copolymer and also polyisoprene, polyisobutylene, and the like." In Example 1 polyethylene is disclosed.
In U.S. Pat. No. 4,226,761 polyethylene is also included in the polyphenylene ether compositions.
While compositions comprising polyphenylene ether (PPO), high impact polystyrene (HIPS), aromatic phosphate flame retardant and polyethylene (PE) possess good physical properties, it has been found that they are difficult to paint in injection molded form, as a result of poor adhesion between lacquer-paint coatings and the PPO/HIPS/aromatic phosphate/PE substrate.
While paint adhesion may be improved simply by removal of the PE from the PPO/HIPS/aromatic phosphate/PE composition, or composite, such removal adversely affects mold release properties during injection-molding as well as impact performance.
It has now been found that if the PE is replaced by a low molecular weight polyamide or a low molecular weight polyolefin glycol, as for example polyethylene glycol or polypropylene glycol, paint adhesion is significantly improved with no loss of mold-release properties, that is, the molded parts do not resist ejection from the mold during injection molding. The novel compositions possess good or improved Izod and Gardner impact strength, and in cases where the polyolefin glycol polymer replaces the polyethylene, the mutual solubility of components of the compositions is increased, with an increased resistance to environmental stress and reduction in the phenomenon known as juicing. Besides serving as a compatibilizer and providing improved blend homogeneity, the polyolefin glycol polymers increase the solvent resistance of the novel compositions.